The prior art is replete with different types of devices and circuits that filter out undesired electrical characteristics from an incoming source of electricity. In the United States of America, most every home and business is supplied with power from a utility company. Typically, the power supplied from the utility company passes through a transformer and is supplied to a building with an alternating current of 120 volts and a nominal frequency of 60 Hz. Although the power at the utility company is generated at these voltages and frequency values, the actual power received at a particular home or business can vary widely depending upon both how the power is transmitted and how the power is used.
Power transmission lines emanating from utility companies are commonly exposed to the elements as they travel from the utility company to a home or business. As such, the power transmission lines are subject to lightning strikes, interference from sun flares, storm damage and the like. All of these occurrences can create abnormalities in the characteristics of the power being transmitted. For example, a lightning strike in a power transmission line can create a large voltage spike in the power being transmitted. If this voltage spike is received by a home or business, the voltage spike can cause catastrophic damage to any electronic load/equipment that receives it. Alternatively, power call be disrupted if the spike causes a circuit breaker to trip.
Similarly, power transmission lines can receive electromagnetic interference (EMI) and/or radio frequency interference (RFI) from natural and manmade sources. The resulting EMI/RFI signals cause noise in the characteristics of the power transmission that can disrupt sensitive electronic circuits that receive such power transmissions.
Power transmissions with undesirable characteristics can also be created by the way power is used in a home or business. Many electronic devices draw a higher current when they are first turned on. This is because the circuits in the electronic device/load are cold and the capacitors in the circuits are not charged. However, soon after the circuit is powered, the current drawn by that circuit can decrease dramatically. As a result, when an electronic device is first turned on, there is an inrush of current, thereby causing a current spike. If multiple electrical devices are all turned on at once, the inrush current spike can be quite large and either cause a circuit breaker to trip or cause damage to the electronic components of those devices that experience the current spike.
Additional undesirable characteristics experienced in power transmission are that of overvoltage and/or undervoltage conditions. An overvoltage condition is a hazardous condition that exists when the voltage of the incoming power is raised over a safe operating upper limit. Similarly, an undervoltage condition is a hazardous condition that exists when the voltage of the incoming power is lowered below a safe operating lower limit. Depending on the duration, the under/overvoltage event can be permanent or last for a substantial period of time. Because of the prolonged nature of an under/overvoltage condition, circuitry designed to merely protect against transient surges is inadequate.
In the prior art, there are many different devices that are used to eliminate adverse characteristics from a power supply. However, many of these devices are designed to filter out only one type of adverse characteristic. For example, there are many types of commercially available surge protector items that can eliminate voltage spikes caused by lightning. Such prior art surge protectors are exemplified U.S. Pat. No. 4,870,534 to Harford (“the '534 Patent”), entitled Power Line Surge Protector, the entirety of which is incorporated herein by reference. However, such prior art surge protection devices do not protect from EMI/RFI signal interference, incidents of inrush current, or the occurrence of under/over voltage conditions.
Similarly, devices exist in the prior art record that are designed to filter EMI/RFI signal interference from power supplies. Such prior art filters are exemplified by U.S. Pat. No. 5,530,396 to Vlatkovic, entitled EMI Input Filter Power Factor Correction Circuits, the entirety of which is incorporated herein by reference. However, such prior art devices do not protect against voltage surges, inrush current surges, or the occurrence of under/over voltage conditions.
Moreover, devices exist in the prior art that are designed to eliminate inrush current surges. Such prior art devices are exemplified by U.S. Pat. No. 4,573,113 to Bauman, entitled Surge Protection System For A D-C Power Supply During Power-up, and U.S. Pat. No. 5,930,130 to Katyl, entitled Inrush Protection Circuit, the entirety of which is incorporated herein by reference. However, such prior art devices do not protect against EMI/RFI signal interference, voltage surges, or the occurrence of under/over voltage conditions.
To date, the most complete system and method for conditioning power received from an AC power supply source and supplying the conditioned AC power to the electronic load/equipment is disclosed in U.S. Pat. No. 6,744,613 to McCook et al. (“the '613 Patent”), entitled System and Method for Filtering Multiple Characteristics from a Power Supply Source, the entirety of which is hereby incorporated by reference in its entirety. While the device disclosed in the '613 Patent provides combined protection against EMI/FRI interference, inrush currents, and transient voltage surges, it does not provide adequate protection against overvoltage and/or undervoltage power conditions.
Finally, while circuits do exists that generally provide protection against over/undervoltage conditions, these circuits are limited to protecting components in direct current (“DC”) circuitry. Such circuits are not easily conformable to devices that receive, condition, and pass along AC power. Thus, the need still exists for a system and method for conditioning power from AC power supply source that can also provide protection from over/undervoltage conditions.